Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$204.62	8.741%	$222.5058	$222.51	$222.50	$222.50
Purchase #2	$28.42	11.260%	$31.6201	$31.62	$31.60	$31.60
Purchase #3	$41.33	7.292%	$44.3438	$44.34	$44.35	$44.30
Purchase #4	$92.41	7.665%	$99.4932	$99.49	$99.50	$99.50
Purchase #5	$129.48	11.309%	$144.1229	$144.12	$144.10	$144.10
Purchase #6	$72.44	5.693%	$76.564	$76.56	$76.55	$76.60
Purchase #7	$102.74	9.553%	$112.5548	$112.55	$112.55	$112.60
7 purchase totals =	$671.44		$731.2046	$731.19	$731.15	$731.20